Optically active enantiomers of 5-hydroxy-3-(4'-hydroxyphenyl)-1,1,3-trimethylindane (also referred to herein as "indane bisphenol") represented by the formula ##STR1## wherein the asterisk (*) used herein represents the single chiral center, have utility as monomers in the chemical synthesis of various chiral polymers. For example, chiral polycarbonates, polyesters, polyurethanes, and polyethers synthesized from optically pure chiral indane bisphenol monomers are disclosed in two commonly assigned U.S. patent applications being filed concurrently herewith and corresponding respectively to Docket Nos. 0953.032 and 0953.028. These optically pure polymers are useful in the fabrication of optoelectronics devices such as chiral waveguides and/or optical materials such as polarizing coatings and filters. Thus, a need exists for a convenient method for producing optically pure enantiomers of indane bisphenol from racemic indane bisphenol.
HPLC methods using columns packed with a chiral stationary phase are frequently employed to separate enantiomers. However, such methods are typically analytical techniques and can often be difficult and expensive to scale up and perform on a commercial scale. Other traditional separation methods, such as fractional crystallization, are often tedious and expensive, and processing problems are frequently encountered in the preparation of enantiomers on a synthetic scale.
Another method often used to resolve racemic mixtures of chiral compounds involves subjecting the mixture to the stereoselective action of various enzymes. Generally, enzymes for use in resolutions should exhibit a high degree of stereoselectivity for catalyzing the reaction of one isomer to the exclusion of others. For example, enzymatic resolution by enantioselective hydrolysis of various ester compounds has been widely employed for the lab-scale, preparative-scale, and industrial-scale production of many optically pure esters.
One class of enzymes, the hydrolases, which includes lipases, proteases, esterases, trypsins, chymotrypsins, and dextranases, for example, is often used in the resolution of enantiomers because they are commercially available at reasonable cost, they do not require expensive cofactors, and some exhibit reasonable tolerance to organic solvents. Additionally, hydrolases are known to catalyze enantioselective hydrolysis of esters. However, one disadvantage of enzyme-catalyzed resolution processes, including those catalyzed by hydrolases, is that there is no way to predict in advance the stereospecificity of a certain genus of enzyme for a given substrate.
Resolution of the enantiomers of the racemic esters of (R,S)(.+-.)-indane bisphenol using any of the aforementioned methods has not heretofore been described. Such a resolution is desirable to prepare substantially pure indane bisphenol enantiomers for use as monomers in the synthesis of chiral polymers. Such chiral polymers are useful in the manufacture of high performance optical materials. A definite need therefore exists for a convenient, economic, and efficient method for separating the individual enantiomers of racemic (R,S)(.+-.)-indane esters to produce on a commercial scale optically active indane bisphenol isomers.